Phone module:
- Audi A6/A8: under the driver’s seat under the carpet
- Porsche: under the passenger’s seat under the carpet, or under the driver’s seat
- In other cases, it is in the trunk, but can be also behind the front seats (cabriolet or sport version cars).
CD changer:
- It is mostly in the trunk, sometimes in the glove box, in rare cases in the center console.
- If the CD changer connection was too far in the car, then you can use the optical extension kit (FOA1PO1) for the installation, which makes it possible to place the hardware of the Gateway to the front part of the car, into the glove box for example.
As an example here is an old Audi 6CD changer and a Porsche phone module.